SQL Pivot String Data - sql

Question

I have a tables in SQL Server: Product
Product Table:
ImageID ProductID
------- ----------
1 P1
1 P2
1 P3
2 S1
2 S2
2 S3
3 M1
This is the output that I need:
ImageID Product1ID Product2ID Product3ID
----------- ---------- ---------- ----------
1 P1 P2 P3
2 S1 S2 S3
3 M1 null null
An ImageID can have maximum 3 ProductID
It is not necessary that all ImageID will have 3 products [eg. ImageID=3]
SELECT ImageID, [Product1ID], [Product2ID], [Product3ID]
FROM
(
SELECT ImageID, ProductID
FROM ProductTable
) AS P
PIVOT
(
max( ImageID)
FOR ProductID IN ([Product1ID], [Product2ID], [Product3ID])
) AS PVT

Answer 1

I would just use conditional aggregation:
SELECT ImageID,
MAX(CASE WHEN seqnum = 1 THEN ProductID END) as Product1ID,
MAX(CASE WHEN seqnum = 2 THEN ProductID END) as Product2ID,
MAX(CASE WHEN seqnum = 3 THEN ProductID END) as Product3ID
FROM (SELET pt.*, ROW_NUMBER() OVER (PARTITION BY ImageId ORDER BY ProductID) as seqnum
FROM ProductTable
) P
GROUP BY ImageID;
The key idea, though, is to use ROW_NUMBER() to enumerate the products.

Answer 2

Your were very close, you just needed to incorporate Row_Number()
Example
Select *
From (
Select ImageID
,Item = concat('Product',row_number() over (partition by ImageID order by ProductID),'ID')
,ProductID
From ProductTable
) src
Pivot (max(ProductID) for Item in ([Product1ID], [Product2ID], [Product3ID])) pvt